The design of magnetic power converters depends on factors including the permeability, loss factor, and size and shape of the magnetic material in the converter. Specifically, the loss for magnetic material usually accounts for 30-40% of the total loss of the converter. Conventional magnetic materials, such as Ferrites and Molydbenum Permalloy Powder (MPP), are known for their low loss characteristics and high frequency operation. Therefore, these magnetic materials may be used in power converters, such as inductors and transformers. However, these magnetic materials suffer from a number of disadvantages, including limited size, brittleness, high loss and high cost.
For example, it is difficult to provide a transformer or inductor useful in high power conversion, such as a system of more than 20 kW, because of the complexity and expense in the formation of Ferrites or powder iron. In addition, conventional materials must be screened in this application. A metal and plastic material chassis is often used to screen electromagnetic emissions, which increases the cost and the weight of the electronic product.
The loss in power conversion can be divided into conductor loss and core loss. The conductor loss, or winding loss, is the resistive loss due to the current passed through the winding around the magnetic material. Because of the current distribution in the conductor at high frequency, this loss can increase dramatically as the frequency increases. The core loss is usually caused by the hysteresis, eddy loss and/or residue loss of the magnetic materials. The hysteresis loss and eddy loss can be decreased by using power iron core for high frequency application. The introduction of polymer into the conventional core could also lower the eddy loss to some extent, which could extend their applications to a broader range at high frequency area.
The technology and engineering domains constantly set demanding requirements of magnetic materials. Recently, polymer bonded magnetic materials have attracted a great deal of attention in the fields of magneto-electrics and magneto-optics. These materials are composed of polymer matrices and magnetic powders, which may be produced using traditional polymer processing methods. Polymer bonded magnetic materials offer significant advantages over conventional materials. For example, polymer bonded magnetic materials can be molded more easily, lowering the cost of manufacturing and of quality control. Nonetheless, the polymer-bonded magnetic materials have not typically been applicable in power conversion or electromagnetic interference. The outstanding work needed in the optimization and the permeability study has prevented developing the materials into a product.
It is desirable to produce a magnetic material that could be easier to form into device cores for application in high power conversion (over 20 kW). Ideally, these magnetic materials would have sufficient flexibility. It is also desirable to manufacture the magnetic material at a low cost. It is further desirable to produce a magnetic material that is light weight. It is also desirable to produce a magnetic material useful for high frequency power conversion, such as over 100 s kHz operation. It is further desirable to that the magnetic material is applicable in power transformers and inductors.